Through independent localized pressure and geometry measurements in vitro in human acetabula, we have demonstrated correlations between global pressure distribution and percent cartilage compression under identical loading conditions. The unloaded cartilage surface is remarkably spherical while the underlying calcified-cartliage, subchrondral bone interface can be quite irregular. We now plan measurements (1) under static conditions with changing load vector direction, and (2) under dynamic conditions to simulate hip joint movement as well as loading. Experiments heretofore in relatively healthy joints will move into comparable studies employing osteoarthritic tissue. In the parallel in vivo study, we will implant similar pressure-instrumented femoral head reconstruction prostheses in consenting humans requiring such procedures; study the pressure distribution from initial insertion on through recovery and normal activity; correlate in vivo data with our in vitro studies; and compare the load vector across the human hip measured internally (by integration of the pressure distribution) with gait analysis predictions based on external kinematic and foot-floor data and a segmental Newtonian model of the moving human.